1. Recent Advances in the Synthesis of Yohimbine Alkaloids
2. J. Shavel, Jr. and H. Zinnes, US Patent 3291800 (1966)
3. Chem. Abstr., 67, 32875p (1967).
4. The compounds described in this paper are named according to IUPAC nomenclature as derivatives of indolo[2′,3′:3,4]pyrido[1,2-b]-isoquinoline. In this system, the 13b-, 1-, 2-, and 3-ring positions correspond to the 3-, 16-, 17-, and 18-positions, respectively, in the older nomenclature based on the natural product yohimbine.